Lizbeth Webb, one of the great forgotten stars of British musical theatre in the 1940s and 1950s, has died aged 86. Known as "the champagne soprano", she was the first to sing one of the BBC's most requested songs of all time, This Is My Lovely Day, written for her by Vivian Ellis and AP Herbert and included in their musical comedy Bless the Bride (1947).

Starting out during the second world war as a teenage singer with dance bands – she worked later with such conductors as Mantovani, Geraldo, Max Jaffa and Vilém Tauský – Webb was discovered by the bandleader Jack Payne and turned into a West End star by the impresario Charles B Cochran in 1946. Over the next 10 years she made her mark as a soprano of great range (often singing in two different registers), vibrancy and vivacity. She was dark, petite and pretty; when Webb burst into tears at a difficult moment in rehearsals, Ellis said that the sight was "no more distressing than watching a lovely waterfall".

Elizabeth Sandra Holton was born in Tilehurst, Reading, the youngest of three children of Frederick and Ethel Holton. Her mother died soon after giving birth, and Elizabeth was raised by an aunt and uncle, Ethel and Alfred Wills Webber. Educated at Hemdean House school and Queen Anne's school, both in Caversham, Berkshire, she took singing lessons from an early age.

Recommended to the BBC, she made her first broadcast, from Ayr, at the age of 16; as a result, Payne hired her to sing with his band and changed her name to Betty Webb. She was soon appearing on leading popular radio shows such as Workers' Playtime, Variety Bandbox and Friday Night Is Music Night.

Cochran cast her in a small role in Ellis and Herbert's first collaboration, Big Ben (1946), a parliamentary satire with an operatic election, directed by Wendy Toye, but when the leading lady, Carole Lynne, dropped out, she took over the role of Grace Green with notable success, changing her name once more, at Cochran's insistence, to Lizbeth Webb.

The same production team fashioned Bless the Bride, an operatic soufflé set in the Victorian era, especially for her talents, pairing her with the French music-hall star Georges Guétary with whom her character sang I Was Never Kissed Before in the shrubbery after eloping with him and deserting a stuffy English fiance. Bless the Bride opened at the Adelphi in the same week as Oklahoma! at Drury Lane.

Bless the Bride ran for around two years, and Webb followed it with a leading juvenile role (opposite Thorley Walters) in Ivor Novello's last musical, Gay's the Word, starring Cicely Courtneidge as a drama school teacher who weirdly falls in with a gang of smugglers. The show started in Manchester in 1949 and fetched up in 1951 at the Saville theatre in London, where it was a big success, despite Noël Coward describing it as "horrible stuff" and Kenneth Tynan languidly remarking that: "If I do not enjoy this, it is probably because I have memories of an aunt who did much the same thing at church socials."

All the same, Webb had another big hit with her romantic ballad Love Is My Reason, and was an obvious choice to play the Salvation Army heroine Sarah Brown in the London premiere of Guys and Dolls at the Coliseum in 1953. The musical was televised and featured in the Royal Variety Show. In the disastrous Jubilee Girl, Webb played a "new woman" who marries a nobleman; she baled out of the touring production – along with the director, the choreographer, five dancers and Marie Lohr – and left the show to flounder miserably at the Victoria Palace, despite Fenella Fielding standing firm.

Webb, who had been briefly engaged to Peter Sellers after she appeared in an episode of The Goon Show on radio, married DH Parker, an RAF pilot. They later divorced. In 1956, after touring in Korea, Cyprus and Libya to entertain the troops, she met and married her second husband, Colonel Guy Campbell, then head of the British military in Tripoli. Campbell received the Military Cross and in 1961 succeeded to his family's baronetcy.

Webb effectively retired but had a notable television appearance alongside Ginger Rogers in Carissima, a 1959 BBC adaptation of a musical by Eric Maschwitz and Hans May, about a cosmetics manufacturer.

In 1960, she and Campbell returned to England, where she continued to make guest appearances on radio and on the popular television comedy shows of Charlie Drake and Dickie Henderson while working in the casting agency of Harry Foster. In 1969, she appeared in a lengthy tour of Franz Lehár's The Merry Widow before opening at the Cambridge theatre in London. Only an injury prevented her from joining in a celebration in 1996 of Ellis's life.

She and Campbell lived for a few years in Marbella, Spain, in the 1970s before returning to England once again and living in Cheltenham. Her husband died in 1993 and Lizbeth settled in London. She is survived by their sons, the artist and illustrator Lachlan Campbell and the actor and opera singer Rory Campbell; four grandchildren; and her brother, Philip.